The testing speed of ultrasonic test objects with an oblique angle of sound incidence in pulse-echo technology is linked to the sound field expansion across the direction of sound propagation of the ultrasonic field emitted by the ultrasonic transducer. Thus, in ultrasonic testing of thin-walled pipes, in which the pipe is “monitored” in the axial direction for suspicious reflections due to flaws in the pipe caused by multiple reflections on the walls of the pipe due to translational and/or rotational relative movements, for example, due a relative spiral movement, between the ultrasonic transducer and the pipe (i.e. test object). The “lower” it is possible to identify defect echoes in the material of the test object or in thin-walled test objects in the case of oblique incidence of sound, despite acoustic damping, the greater the distance away from the point of sound incidence, the faster the complete detection of the test object can be.
Due to the use of acoustic transducers having a greater sound-emitting (i.e. acoustically active) area, there is the possibility of mechanically enlarging the sound field expansion. However, this procedure may cause the device to become expensive and also the requirements of acoustic coupling between the test object and the ultrasonic transducer becomes higher. However, a greater sound field expansion permits more rapid testing of a workpiece due to possible cost savings.
There is therefore a demand for a method for ultrasonic testing according to the pulse-echo method, in which detection of defects is improved and, in particular, in which complete detection of the test object can be carried out more rapidly.